Currently, as a catalyst for an electrode of a fuel cell, a platinum catalyst is used. However, there are many problems to be solved. For example, the reserves of platinum are limited. In a polymer electrolyte fuel cell (PEFC), the use of platinum increases cost. In an air cell, the use of platinum increases cost, and in addition, a chemical reaction such as decomposition of an electrolyte solution caused by platinum occurs. Therefore, an alternative technology that does not use platinum has been developed.
Specifically, for example, in Patent Literature 1, there is disclosed an electrode catalyst for a fuel cell formed of a carbonized material having a shell-like structure.